Sorry about that. I don't know what the right advice is, but if I were in your place I would have an honest chat with your old CEO. There's nothing to lose by being honest about what you want (but I would steer clear of being too negative about where you are at). It might be the chance of a lifetime and it might not but it definitely sounds more awesome because where you are is shitty. So - tell them what you need to get by, see where they are at. It might open a door, it might not be the right time. But you are miserable so start looking / talking and see what happens.

Best of luck!